UIUC MCB 354 Exam QUESTIONS AND
CORRECT ANSWERS
What is the starting point for carbon atom labeling in organic chemistry? - CORRECT ANSWER
Start from the carboxyl carbon (C=O) and label as α, β, γ, etc.
Which amino acid is the only non-chiral amino acid? - CORRECT ANSWER Glycine
What system is used to denote chirality in organic chemistry? - CORRECT ANSWER R/S
system
What system is used for chirality in biochemistry? - CORRECT ANSWER D/L system, based
on glyceraldehyde
What does a low pKa value indicate about a group? - CORRECT ANSWER It is acidic and
easily deprotonated.
What is the pKa of the carboxyl group in glycine? - CORRECT ANSWER Approximately 2.34
What is the isoelectric point (pI) of glycine? - CORRECT ANSWER Approximately 5.97,
calculated as pI = (pK₁ + pK₂) / 2
What amino acid has three ionizable groups and what are its pKa values? - CORRECT ANSWER
Histidine; pKa values: Carboxyl ~2, Amino ~9, R-group (imidazole) ~6.0
What is a dipeptide? - CORRECT ANSWER A peptide consisting of 2 amino acids.
What is the directionality of peptide synthesis? - CORRECT ANSWER From the N-terminus
(H₃N⁺) to the C-terminus (COO⁻).
What are conjugated proteins? - CORRECT ANSWER Proteins that have prosthetic groups,
such as lipoproteins, glycoproteins, metalloproteins, and flavoproteins.
, What is the Merrifield method used for? - CORRECT ANSWER Chemical synthesis of small
proteins.
What stabilizes the native conformation of proteins? - CORRECT ANSWER Weak
noncovalent interactions and covalent bonds, such as disulfide bonds.
What defines the secondary structure of proteins? - CORRECT ANSWER The local folded
structures, such as α-helices and β-sheets.
What is the Ramachandran plot used for? - CORRECT ANSWER To show allowed Φ/Ψ angles
in proteins.
What is the structure of myoglobin? - CORRECT ANSWER A monomeric protein with 153
residues and one heme group.
What is the role of His93 in myoglobin? - CORRECT ANSWER It is the proximal histidine
that binds Fe²⁺.
What does the association constant (Ka) represent? - CORRECT ANSWER The affinity of a
ligand for a protein; high Ka indicates high affinity.
What does a low dissociation constant (Kd) indicate? - CORRECT ANSWER High affinity
between a ligand and a protein.
What is the significance of the hydrophobic effect in protein folding? - CORRECT ANSWER
Nonpolar groups cluster to reduce the solvation layer, increasing entropy.
What are protein motifs? - CORRECT ANSWER Small, recognizable 3D structural units
shared among proteins.
What is the definition of protein domains? - CORRECT ANSWER Distinct structural and/or
functional units within a protein.
CORRECT ANSWERS
What is the starting point for carbon atom labeling in organic chemistry? - CORRECT ANSWER
Start from the carboxyl carbon (C=O) and label as α, β, γ, etc.
Which amino acid is the only non-chiral amino acid? - CORRECT ANSWER Glycine
What system is used to denote chirality in organic chemistry? - CORRECT ANSWER R/S
system
What system is used for chirality in biochemistry? - CORRECT ANSWER D/L system, based
on glyceraldehyde
What does a low pKa value indicate about a group? - CORRECT ANSWER It is acidic and
easily deprotonated.
What is the pKa of the carboxyl group in glycine? - CORRECT ANSWER Approximately 2.34
What is the isoelectric point (pI) of glycine? - CORRECT ANSWER Approximately 5.97,
calculated as pI = (pK₁ + pK₂) / 2
What amino acid has three ionizable groups and what are its pKa values? - CORRECT ANSWER
Histidine; pKa values: Carboxyl ~2, Amino ~9, R-group (imidazole) ~6.0
What is a dipeptide? - CORRECT ANSWER A peptide consisting of 2 amino acids.
What is the directionality of peptide synthesis? - CORRECT ANSWER From the N-terminus
(H₃N⁺) to the C-terminus (COO⁻).
What are conjugated proteins? - CORRECT ANSWER Proteins that have prosthetic groups,
such as lipoproteins, glycoproteins, metalloproteins, and flavoproteins.
, What is the Merrifield method used for? - CORRECT ANSWER Chemical synthesis of small
proteins.
What stabilizes the native conformation of proteins? - CORRECT ANSWER Weak
noncovalent interactions and covalent bonds, such as disulfide bonds.
What defines the secondary structure of proteins? - CORRECT ANSWER The local folded
structures, such as α-helices and β-sheets.
What is the Ramachandran plot used for? - CORRECT ANSWER To show allowed Φ/Ψ angles
in proteins.
What is the structure of myoglobin? - CORRECT ANSWER A monomeric protein with 153
residues and one heme group.
What is the role of His93 in myoglobin? - CORRECT ANSWER It is the proximal histidine
that binds Fe²⁺.
What does the association constant (Ka) represent? - CORRECT ANSWER The affinity of a
ligand for a protein; high Ka indicates high affinity.
What does a low dissociation constant (Kd) indicate? - CORRECT ANSWER High affinity
between a ligand and a protein.
What is the significance of the hydrophobic effect in protein folding? - CORRECT ANSWER
Nonpolar groups cluster to reduce the solvation layer, increasing entropy.
What are protein motifs? - CORRECT ANSWER Small, recognizable 3D structural units
shared among proteins.
What is the definition of protein domains? - CORRECT ANSWER Distinct structural and/or
functional units within a protein.
